Ultrawideband (UWB) is becoming an attractive radio access solution for wireless communications, particularly for short and medium range applications. According to the modern definition, any wireless communication technology that has a bandwidth wider than 500 MHz or a fractional bandwidth greater than 0.2 can be considered a UWB system. Ultra-wideband (UWB) microwave systems are finding application in the form of sensors for speech aides, impulse radio, as well as respiratory and cardiovascular monitoring. The Federal Communication Commission (FCC) defines UWB as an intentional radiator with an instantaneous 10 dB-fractional and total bandwidth of at least 0.2 and 500 MHz, respectively. This bandwidth is achieved primarily by radiating short pulses that are derived from a basic Gaussian pulse shape.
Tunable pulse generators are useful in UWB radar and radiometric measurement because they provide a platform for optimizing the absorbed and reradiated power of an isolated target. As a result, power optimization may be required for enhancing discrimination and evaluation of electrical characteristics associated with a target. Consequently, a tunable generator can be used to achieve varying penetration depth, radiation intensity and range resolution by controlling the shape and center frequency of the spectrum, because of a targets frequency-dependent electrical property. Thus, tunable pulse generators provide a valuable tool for research requiring UWB measurement of the electrical properties of materials.
One approach for designing a tunable pulse generator is based upon switching in sequential sections of transmission lines to combine short pulses or vary the circuit impedance. These systems often require a number of discrete components in addition to power biasing for each section. Moreover, they often loose their Gaussian symmetry as more pulses are combined for increasing its width.
Accordingly, what is needed in the art is a UWB tunable generator that utilizes fewer components, maintains Gaussian symmetry in the generated signal and allows for easier assembly and a reduction in cost.